* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Presentation (englis..
Chirp spectrum wikipedia , lookup
Mechanical filter wikipedia , lookup
Spectrum analyzer wikipedia , lookup
Power inverter wikipedia , lookup
Mathematics of radio engineering wikipedia , lookup
Nominal impedance wikipedia , lookup
Ringing artifacts wikipedia , lookup
Voltage optimisation wikipedia , lookup
Utility frequency wikipedia , lookup
Spark-gap transmitter wikipedia , lookup
Audio power wikipedia , lookup
Mains electricity wikipedia , lookup
Wien bridge oscillator wikipedia , lookup
Audio crossover wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Distribution management system wikipedia , lookup
Alternating current wikipedia , lookup
Buck converter wikipedia , lookup
Three-phase electric power wikipedia , lookup
Variable-frequency drive wikipedia , lookup
Opto-isolator wikipedia , lookup
Zobel network wikipedia , lookup
Switched-mode power supply wikipedia , lookup
SENDER SENDER S.A. SENDER A.M. Transmitters SENDER SENDER S.A. • Company was created in 1997 by a group of engineers and technitians with long experience in Solid state A.M. Transmitters. • Located in Santiago Chile, with 25 employes. 40% of them are shareholders. • Main activity: Design and manufacturing of A.M. transmitters, antenna tuning units, duplexers and triplexers. • First transmitter in operation Nov 1997. • Transmitters sold up to now:127 from 1 KW to 12.5 KW. SENDER Product Line AM 1500 SS 1.5 KW/1.1 KW, single phase / 2 power amplifiers AM 3000 SS 2.25 KW/3KW, single phase or 3 phase / 4 power amplifiers. AM 7500 SS 5.5 KW/ 7.5 KW, 3 phase or single phase / 7 power amplifiers. AM 15000 SS 11 KW/13 KW,3 phase / 14 power amplifiers AM 25000 SS 22 KW/26KW, 3 phase / 28 power amplifiers A.T.Us for 1.5 KW, 3 KW,7.5 KW, 13 KW and 26 KW SENDER Product highlights • Solid State. Modular / redundant architecture • High efficiency. PWM & class D R.F. amplifiers • Hot plug in power amplifiers with Mosfets. • Simple design with standard components. • Totally rustproof cabinet made of iridated aluminum with stainless steel hardware. • Excellent specs and audio quality. • Outstanding factory support. • Very competitive price. SENDER Basic specifications Frequency range: .53 MHZ to 1.7 MHZ. Input voltage: 110V or 220 V single phase, 220V or 380V 3 ph +or - 10%. Line frequency 47HZ to 63 HZ. Efficiency: 75% or better for single phase transmitters, 80% or better for 3 phase transmitters. Frequency response: Better than +or- 1 dB 30 Hz to 10 KHZ. Distortion: Less than 1% at nominal power and 90% modulation. Harmonics and spurious:- 73 dB or better for AM 1500 SS, - 80 dB or better for other models. SENDER Frequency stability:+- 5 Hz. Output impedance: 50 Ohm Dimentions and weigths: AM 1500 SS W=44 cm,H=62.5cm D=60 cM , 100 Kg. AM 3000 SS W=44 cm,H=65.5cm D=60 cM , 160 Kg. AM 15000 SS W=80 cm,H=181cm D=81 cM , 500 Kg. SENDER Standard features: 2 power level with independient adjustment and modulation autotracking. Start, stop,power level selection and power level adjustment remotely controled. Automatic alarm reset. Positive and negative limiter. SENDER Basic block diagram A1 Synth A2 Combiner PWM An PWR Supply Control Output Filter Out SENDER Relationship with RICHARDSON ELECTRONICS • Exclusive representation for Asia and other specific countries. • Joint project to manufacture transmitters in U.S.A. • Sender sells Omnicast F.M. Transmitters in Latin America. • Excellent level of personal contacts . SENDER Near future projects • FCC type acceptance. • Frequency agile 1.5 KW transmitter. • IBOC compatibility. • Inboard audio processor and modulation monitor. • Higher power amplifiers SENDER Reliability in A.M. stations SENDER Introduction Station Concept • Harmonic set of: – Transmitter – Radiating system – Energy System – Auxiliary Equipment SENDER Experience with stations using Solid State A.M. Transmitters • Very high reliability if precautions related with the following topics are considered: Antenna discharges A.C. Source transients and discharges A.C. Source voltage limits Load stability Interference from nearby stations Reliability is reduced in unprotected stations SENDER Basic elements of a station ANTENNA STL RX Audio & Rem. Ctrl. RF H.V TRANSF. DISTR. BOARD TX T.P. ATU A.C. GROUND PLANE SENDER TRANSMITTER BASIC BLOCKS • • • • • • • POWER SUPPLY PWM MODULATOR R.F. DRIVER CLASS D or E R.F. OUTPUT FILTER CONTROL,PROTECTIONS,SIGNALING EXTERNAL INTERFACE SENDER PWM MODULATOR • GENERATES D.C + A.C. VOLTAGE FOR THE R.F. AMP. • SWITCHING DEVICE, HIGH EFFICIENCY • A FILTER IS NEEDED TO ELIMINATE SWITCHING FREQUENCIES • CONMUTATION FREQUENCY IS 72 KHZ. SENDER PWM (PULSE WIDTH MODULATION) SIMPLIFIED DIAGRAM: R.F. AMPLIFIER D.C. SUPPLY Switch (Mosfet) PWM FILTER LOAD SENDER PWM BASIC OPERATION • Between 1) y 4) duty cycle is increased • Mean voltage in the load increases proportionally • A filter is required to remove high frequency components F = 72 kHz PWM waveform 1) S V 2) RL 3) 4) Filtered output voltage SENDER PWM Frequency spectrum Amplitude D.C Component PWM 0° Audio 72 kHz 144 kHz Frecuency SENDER PWM Frequency spectrum Amplitude D.C. component PWM 180° Audio 72 KHZ components out of phase 72 kHz 144 kHz Frecuency SENDER PWM filter diagram SENDER PWM filter frequency response SENDER PWM filter response sensibility to load changes Rload +/- 15% SENDER Load change consequences • With reduced load (Rload< Rnominal) transmitter will produce high frequency submodulation • With increased load (Rload>Rnominal) transmitter will show high frequency overmodulation • Distorsion will increase if filter is not propperly loaded. SENDER Modulated class D R.F. Amplifier. +V T1 T2 PWM filter RL T3 T4 SENDER Class D r.f. Amplifier diagram SENDER Class D Bridge parasitic elements V+ Cgd Cgd Cds Cgs Cds Cgs RL Cgd Cgd Cds Cgs Ciss = Cgs + Cgd Cds Cgs Crss = Cgd Coss = Cds + Cgd SENDER Mosfets drive Vgs V+ T1 RL Dead time T3 Vgs(thr) time T2 T4 Vgs peak = 13V SENDER R.F. drive circuit • Ls and Cs series resonant • Lp paralel resonant with mosfet input capacitance (Partially) Ls Cs MOSFET drive Drive signal Lp SCgs SENDER Class D bridge current paths V+ T1 T2 RL V+ T3 T1 T4 T2 RL T3 T4 SENDER Class D bridge undisered current paths. V+ T1 T2 RL V+ T3 T1 T4 T2 RL T3 T4 SENDER Class D Amplifier basics. • Low impedance driver required for: – Fast switching – Low Vgs modulation by Crss • Tuned load to produce sinusoidal current • High efficiency (>95 %) • Duty cycle should be < 0.5 – Avoid transversal currents – Coss charge and discharge through Rl Class D R.F. Amp typical waveforms. SENDER SENDER MOSFET characteristics • No secondary breakdown • positive temperature coeff. Of Rdson (Simplify parallel operation) • Voltage controled device (Vgs) • Driver impedance dependent switching times. • Intrinsic antiparallel diode SENDER IRFP350 MOSFET • • • • • • Rdson = 0.3 ohms Vdss = 400 Vdc Vgs = +/- 20 Vmax Vth = 3 V Vsat = 9 V Id = 16 A @ Tc=25ºC 10 A @ Tc=100ºC Idmax = 64 A Capacitance @ f=1MHz, Vds=25V , Vgs=0V – Ciss = 2600 pF (2400 pF for Vds>40V) – Coss = 660 pF (200 pF for Vds>40V) – Crss = 250 pF (50 pF for Vds>40V) SENDER Class D amplifier example SENDER SENDER Class D Simulation (1/2 bridge,Vmax<400x.75/2.5) • Cicuit data – – – – Vdc = 110 V F = 1600 kHz d = 0.43 Transistor IRFP350 • • • • Rdson = 0.3 ohms Ton = 16 ns Toff = 40 ns Coss = 200 pF – L2 = 7.04 uH – C2 = 1.55 nF • Operational data – RL = 15 ohms – Po = 132.36 W – h = 97.93 % •Transistor stresses – Vmax = 110.81 V – Imax = 4.12 A – Pdis = 0.70 W x2 (1.4 Wtotal) *Simulated with HB plusfrom Design Automation SENDER Class E Amplifier diagram SENDER Class E amplifier example SENDER Class E amplifier basics. • R.F.Choke large enough to produce constant current • High Q series resonant circuit to produce sinusoidal current • Vds y dVds/dt =0 prior to starting conduction • High efficiency (>95%) – if special high voltage transistors with low Rdson are used SENDER Clase E Waveforms SENDER Clase E Simulation (Vmax<400x.75/2.5) • Circuit Data – Vdc = 33 V – F = 1600 kHz – d = 0.48 – Transistor IRFP350 • Rdson = 0.3 ohms • Ton = 16 ns • Toff = 40 ns • Coss = 200 pF – L1=12.3uH L2=3.7uH – C1= 4.1nF C2=4.9nF • Operational Data – RL = 7.3 ohms – Po = 125.27 W – h = 90.53 % • Transistor stresses – Vmax = 118.79 V – Imax = 9.84 A – Pdis = 6.55 W x2 (13.1 Wtotal) *Simulated with HEPA Plus from Design Automation SENDER Passband Output filter • Reduce R.F. Harmonics – High third harmonic att > 80 dB – Medium second harmonic att. > 40 dB – Higher harmonics att > 70 dB • Permits impedance matching between amplifier and load. • Atenuates low frequency components (Lightning protection) SENDER Output filter • Design oriented to protect R.F.amplifier – Low frequency attenuation – Inductor input – Strategically located sensors: • Spark Gap °Transient suppressor • SWR °Overpower • Overcurrent °Phase • Input transient suppressor(Active or pasive) SENDER Output filter diagram SENDER Output filter frequency response SENDER Real and imaginary part of filter input impedance SENDER Protections integrated in the output filter SENDER SENDER SENDER Posible Transmitter Agresions • Antenna – Impedance change and discharges • A.C. Supply – Voltage variation and transients • Program signal – Level variations and transients • Ground – Transfered potentials and high ground currents SENDER Antenna related problems • Impedance change – Low heigth antennas are particularly unstable • Restricted bandwidth • Interference from other stations • Discharges SENDER Short antenna example 60 m tower operating at 700 kHz ZL = 8 - j160 Q = 20 Electrical length = 50.4º SENDER Type T -90º Standard A.T.U. 4.55uH 40.9uH j180 j20 Zin 50+j0 11.37nF -j20 ZL 8-j160 SENDER A.T.U.Sensibility to antenna impedance changes Change in XL (+/- 10 ohm=6%) if ZL=8-j150 Zin=19.5-j24.4 if ZL=8-j160 Zin=50+J0 if Zl=8-J170 Zin=19.5+j24.4 Change in RL ( +/- 1 ohm =12.5%) if ZL=7-j160 Zin=57.1+j0 if ZL=9-j160 Zin=44.4+j0 RL and XL simultaneous variation if ZL=7-j150 Zin=18.8-j26.8 if ZL=7-j170 Zin=18.8+j26.8 if ZL=9-j150 Zin=19.9-j22 if ZL=9-j170 Zin=19.9+j22 SWR=3.26 SWR=1 SWR=3.26 SWR=1.14 SWR=1.14 SWR=3.52 SWR=3.52 SWR=3.10 SWR=3.10 SENDER Complex A.T.U. (dual T) -j44.9 Zin 50+j0 -j92.5 j50.5 20-J13 -20° Variations in XL if ZL=8-j150 if ZL=8-j160 if ZL=8-j170 j5 j145 ZL 8-j160 j37 20° Zin=50+j62.5 Zin=50+j0 Zin=50-j62.5 SWR=3.26 SWR=1.00 SWR=3.26 Note: SWR of 8+/-j10 refered to a 8+j0 is 3.26 ! SENDER Load ladder RF amplifiers 1 50 Ohm Z1 combiner n filter Antenna A.T.U. Zn 15 Ohm Extreme values for SWR 1:1.5, refered to 50 Ohm, are: 33.3+j0 75.0+j0 50-j20.4 50+j20.4 SENDER Load variation effects Class D amplifier Load VSWR (%) 15 15-j6.1 15+j6.1 22.5 10.0 1 1.5 1.5 1.5 1.5 97.93 96.55 97.83 98.47 96.94 P (1/2 bridge) 132.36 151.92 93.00 96.08 165.02 Vmax (V) Imax (A) 110.81 109.80 110.83 110.02 110.84 4.12 57.77 3.44 13.89 5.66 SENDER A.T.U. And amplifier stresses 20°+20° 90° A)ZL=50-J62.5 Eff=93.5% Po=4.5W Ip=15.5A B) ZL=50+J62.5 Eff=90.9% Po=2.02W Ip=1A C) ZL=19.5+J24.4 Eff=84% Po=44W Ip=105A D)ZL=19.5+J24.4 Eff=93.8% Po=395W Ip=73.7A SENDER Class D waveforms Ro=15 VSWR=1:1 SENDER Class D waveforms Ro=15-j6.1 VSWR=1:1.5 SENDER Class D waveforms Ro=15+j6.1 VSWR=1:1.5 Class D waveforms Ro=22.5 VSWR=1:1.5 SENDER SENDER Class D waveforms Ro=10.0 VSWR=1:1.5 SENDER Atmospheric discharges • At the antenna • In A.C.lines • In telephone lines Characteristics Imax: 200 kA Itypical: 10 a 20 kA dI/dT typical: 10 kA/useg Risetime: 2 useg Decay time:40 useg to 50% SENDER Criteria to minimize damages • Disipators – Avoid charge acumulation using sharp points – or active systems • Well designed grounding system – Low impedance direct paths – High impedance undesired paths – Radial equipotential conections – Antenna and ground conection closely located at TX SENDER Discharge probability function N = 15 L (C·H+h)2 ·10-6 N = Discharges per year L = Ceraunic level (Nº of days per year when thunderstorms are heared) C = Site topographic index (0 to 0,3) H = Site mean heigth above surroundings (1 to2 km) h = Antenna heigth Example: C=0.1 L=50 H=100m h=120m N = 12.7 discharges per year. SENDER Discharge current circulation 1. Strike 2. Antenna 3. Discharge through the antenna 4. Guy 5. Isolator 6. Spark gap 7. Ground rod 15 8. Base insulator 9. Cnecting Loop 11. A.T.U. isolator 12. A.T.U. 13. Ferrite core 14. Coaxial cable 15. Discharge current in caxial cable 16. A.T.U. Spark gap 17. Disipator 17 1 3 2 4 14 13 12 11 16 9 5 8 6 7 10 SENDER Equipment Instalation Reference ground Coaxial cable A.C. Line transient protector A.C. mains Panelboard Ferrite toroids Ground to auxiliary equipment Transmitter A.C. line Building ground SENDER Ground system equivalent circuit SENDER Discharge voltages and currents Interference 1.- Intermodulation products are generated 2.- SWR protection is desensitized 3.- Dangerous voltages at the R.F. Amplifier and output filter maybe generated. SENDER SENDER Transmitter Protections •A.C.input Overload Short cicuit Transients Overvoltage Undervoltage Assimetry •D.C.supply Overload Transients Failure • R.F. Overcurrent SWR Phase overpower Transients • Internal R.F. Drive Temperature PLL SENDER Factory tests to ensure transmitter reliability • Power amplifiers – Long time operation at 150% modulation • Output – – – – Open cicuit Short circuit Simulated lightning strike SWR • A.C. input – Phase failure – Simulated transient – Voltage variationSENDER SENDER Conclusions Reliability in a transmitting sytem is a function of • Transmitter intrinsic reliability – Power stages regimes much lower than devices limits – Simple low power stages with low number of components • Rational protections adjustment SENDER Conclusions • High quality station engineering – A.C. Transient protection – Antenna discharges protection – Well dimentioned and coordinated grounds. – Stable radiating sysytem. – Interference filtering • Coordination with the manufacturer SENDER Recomended instrumentation for test and adjustment 1.- To measure resonance: 1.1 R.F.Generator 1.2 Oscilloscope or spectrum analyzer 2.- To measure R.F.impedance: 2.1 R.F. bridge (General Radio 1609 or Delta OIB-3) 2.2 R.F. generator (Delta RG3-A or similar) 2.2 Spectrum analyzer (HP 8553B or similar) or detector included in RG3-A SENDER 2.3 An H.P. vector impedance meter may be used instead of 2.1,2.2 and 2.3 3.- To measure power: 3.1 R.F. Dummy load,non inductive or with a tuning network to adjust it to 50+J0 Ohm. 3.2 R.F. Ammeter (Delta TC-1 or similar) or R.F. Wattmeter 4.- To measure frequency response and distortion: 4.1 General purpose oscilloscope, 2 channel 4.2 Audio analyzer (Audio precision Portable One or similar) 4.3 Modulation monitor (H.P. 8901 A or B , Belar AMM3, TFT 923 A.M. or similar.) SENDER 5.- To measure spectrum.5.1 Spectrum analyzer 100KHZ.to 50 MHZ or more TEK 2711, H.P. 8553B plus display unit or similar). 5.2 R.F. atenuator. 5.3 OPTIONAL. Notch filter to remove the carrier frequency and avoid intermodulation 6.- To check efficiency. 6.1 A.C. Analyzer.(To measure A.C. voltage, current, power and power factor SENDER 7.- To measure transmitter carrier frequency. 7.1 Digital frequency meter up to 10 MHZ. Or higher frequency, time base 1 P.P.M. or less. 8.- To measure temperature. 8.1 Infrared temperature measuring unit with suitable digital multitester. (Fluke). 9.- For general voltage and current measurements: 9.1 True RMS digital multimeter, suitable to operate in high R.F. fields. (Our best experience is with Fuke Digital multimeters.) SENDER 10.- For long run test. 10.1 USASI Noise generator. (Delta SNG-1). SENDER SENDER Pablo Phillips D. Agosto 1999